Antiknock mixtures



Patented Feb. 7, 1.950

AN TIKNOCK MIXTURES George Calingaert, Detroit, Mich., assignor to Ethyl Corporation, New York, N. Y., a corporation of Delaware No Drawing. Application November 20,1948, Serial No. 61,307

8 Claims.

This invention relates to chloroand promoethers for use as scavengers with lead antiknock compounds. The bromoethers may be used alone in leaded fuels generally, and are preferred for use in aviation fuels. According to Bartholomew Patent No. 2,398,281, issued April 9, 1946, a preferred leaded motor fuel contains both bromoand chlorohydrocarbon scavengers. For this use my invention is a mixture of a bromoether with a chloro-scavenger or a chloroether with a bromoscavenger.

Scavengers are materials employed with lead antiknock compounds in fuels for internal combustion engines to produce, during combustion, volatile lead compounds which are exhausted from the engine. Scavengers reduce the amount of less volatile lead compounds which otherwise form during combustion and collect on engine parts. For satisfactory operation of an engine employing leaded gasoline, it is essential that a scavenger 'be used. Commercially used scavengers are ethylene dib-romide and ethylene dichloride.

It has generally been believed that in an engine cylinder all scavengers containing a given quantity of a specific halogen are equally efficacious. This property of unit effectiveness within the cylinder is called intrinsic scavenging efficiency, and it varies widely for different halogen compounds. Other desirable properties of scavengers include stability when stored in admixture with lead antiknock compounds, miscibility with lead antiknock compounds, freedom from reduction in effectiveness of lead antiknock compounds,

and volatility giving a suitable pattern of distribution in the engine relative to that of lead antiknock compounds under the range of intake manifold conditions encountered in service.

It is an object of my invention to provide a new class of scavengers having not only good intrinsic scavenging efficiency but also other properties desirable for commercial use.

My invention is in the use as scavengers of chloroand bromoethers, preferably chloroand bromoalkyl ethers having not more than one halogen atom attached to any carbon atom and having a vapor pressure at 50 C. above 0.2 millimeter of mercury.

Among the halogenated ethers within the scope of my invention are the following:

[3,s-dibromodiethyl ether B-loromoethyl-fi-bromoisopropyl ether l9,,6'-dibromodlisopropyl ether a-bromobutyl-p-bromoethyl ether a-bromobutyl-fi-bromoisopropyl ether 13,-5'dichlorodiethyl ether fl-chloroethyl-c-chloroisopropyl ether fi,p'-dichlorodiisopropyl ether u-chlorobutyl-fi-chloroethyl ether s-chlorobutyl-fi-chloroisopropyl ether My scavengers in admixture with lead antiknock compound have been incorporated in gasoline and the resulting fuel used in operations in engines. At the end of each period of operation, examination of those engine parts which are adversely affected in the absence of a scavenger showed that my compounds were always efiective scavengers and were at least as good as those now in commercial use in all respects and in some respects better. For example, my scavengers substantially decreased the exhaust valve deposits.

The quantity of scavenger theoretically required for reaction with the lead to form the lead halide, which quantity is two atoms of halogen per atom of lead, is called one theory of halogen. Present practice is to use one theory of bromine in aviation fuels, While for motor fuels one-half theory of bromine plus one theory of chlorine is used.

To illustrate that in some engines under certain conditions my scavengers have an intrinsic scavenging efficiency superior to those heretofore used, results may be reported from operation of single-cylinder, aviation-type engines, comparing B,;8-dibromodiethyl ether with ethylene dibromide. Under comparable conditions for both scavengers the fi fi-dibromodiethyl ether produced only about 83% of the amount of combustion chamber deposit that was found with ethylene dibromide. Also a reduction was found in deposits on the exhaust valves and spark plugs.

In addition to good intrinsic scavenging efficiency, my compounds possess the other desirable properties mentioned above. For example, for use in certain engines, especially in certain high-output aviation engines, I have found that the scavengers of my invention have evaporation characteristics under the conditions existing in the intake manifold close to those of tetraethyllead. This insures good distribution of the scavenger relative to tetraethyllead between the different cylinders of the engine and avoids the harmful effects caused either by an excess or a deficiency in the theories of halogen for the lead in any cylinder. 0n the other hand, ethylene dibromide and ethylene dichloride have vapor pressures so much higher than that of tetraethyllead that they tend to give relatively poor patterns of distribution. Measurements made during operation of an engine show the marked superiority of my scavengers to ethylene dibromide and ethylene dichloride in this respect.

To illustrate the relative quantities of various scavengers present in the liquid portion of the fuel flowing along the wall of the manifold, a currently-produced eight cylinder, valve-inhead automotive engine was used in which the liquid flowing along the walls of the manifold branches of each pair of cylinders was collected for analysis. A considerable proportion of the total tetraethyllead content of the input fuel was found in this unevaporated liquid, but when ethylene dibromide was used, the concentration of that scavenger in the liquid was only 0.05 theory. From these results a difierent pattern of distribution of tetraethyllead and ethylene dibromide to the cylinders would be expected, and this was confirmed in other operatic-n of the same engine. In contrast, in operation with (fi,/3'-dibrom0d.iethy1 ether) the manifold liquid contained 0.75 theory of the scavenger, which is near enough to the ideal value to assure the attainment of very close to 1.00 theory in the total input to each cylinder. This performance illustrates the improvement in distribution relative to the lead anti-knock compound which can occur with my scavengers.

The storage stability of antiknock fluids containing scavengers is highly important in the shipping and storage of such fluids, either alone or in gasolines. When the antiknock fluid decomposes, lead salts are either precipitated or I.

remain in solution in the fluid, from which they may precipitate when the fluid is blended with gasoline. Decomposition is accompanied by evolution of gas which causes pressure to 'be built up in the containing drum or tank car. The halogenated ethers of my invention are generally superior to ethylene dibromide and ethylene dichloride in respect to the storage stability of the antiknock fluid.

Miscibility of scavengers with lead antiknock compounds and freedom from reduction in the effectiveness of lead antiknock compounds are important commercially. My scavengers generally are satisfactory in these respects.

My scavengers may be used with lead compounds other than tetraethyllead, such as tetrapropyllead, dimethyldiethyllead, and methyltriethyllead. It is customary to make a blend of the lead antiknock compound and the scavenger and then to add this mixture to a gasoline. However, the scavenger and the antiknock compound may be added separately to the fuel. The concentration of my scavengers is not critical, and

4 therefore is not so limited. For aviation fuels, best results have been obtained with proportions varying from 0.8 theory to 1.5 theories, and a wider variation may be used. For motor fuels I recommend the proportions of scavengers set forth in Bartholomew Patent No. 2,398,281.

My scavengers may be used in admixture with one another as well as in admixture with other scavengers.

I claim:

1. An an'tiknock composition consisting essentially of leadalkyl antiknock compound and a scavenger in an amount sufficient to reduce lead deposits in an engine by forming volatile lead compounds, a principal active scavenging ingredient of which is a halogenated ether having a vapor pressure at 50 C. above 0.2 millimeter of mercury selected from the class of brominated and chlorinated lower alkyl ethers.

2. The composition of matter of claim 1 wherein the ether is a dibromoalkylether;

3. The composition of matter of claim 1 wherein the ether is a dichloroalkylether.

4. The composition of matter of claim 1 wherein the ether has no more than one halogen atom attached to any carbon atom.

5. The composition of matter of claim 1 wherein the lead alkyl is tetraethyllead and the ether is {3,5-dibromodiethylether.

6. The composition of matter of claim 1 wherein the lead alkyl antiknock compound is tetraethyllead and the ether is ;6,/3-dichlorodiethyl ether. 1

7. An antiknock composition consisting essentially of tetraethyllead and a mixture of scavengers, the principal active ingredients of which are a brominated lower alkyl ether and a chlorinated lower alkyl ether, each of said ethers having a vapor pressure at 50 C. above 0.2 millimeter of mercury and each of said scavengers present in an amount sufficient to reduce lead deposits in an engine by forming volatile lead compounds.

8. The composition of matter of claim 7 wherein the brominated ether is c,fi-dibromodiethyl ether and the chlorinated ether is fi,/3dichlorodiethyl ether.

GEORGE CALINGAERT.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,668,022 Midgley, Jr. May 1, 1928 2,364,921 Shokal Dec. 12, 1944 2,398,281 Bartholomew Apr. 9, 1946 

1. AN ANTIKNOCK COMPOSITION CONSISTING ESSENTIALLY OF LEADALKYL ANTIKNOCK COMPOUND AND A SCAVENGER IN AN AMOUNT SUFFICIENT TO REDUCE LEAD DEPOSITS IN AN ENGINE BY FORMING VOLATILE LEAD COMPOUNDS, A PRINCIPAL ACTIVE SCAVENGING INGREDIENT OF WHICH IS A HALOGENATED ETHER HAVING A VAPOR PRESSURE AT 50*C. ABOVE 0.2 MILLIMETER OF MERCURY SELECTED FROM THE CLASS OF BROMINATED AND CHLORINATED LOWER ALKYL ETHERS. 